An intrabuccally rapidly disintegrating tablet has been noticed recently, which is produced by reducing a lubricant powder included therein or by excluding a lubricant powder therein at all in order to quicken the disintegration time of the tablet so that the tablet can be disintegrated in the buccal cavity when contacting with saliva.
As a production method of such an intrabuccally rapidly disintegrating tablet, already disclosed is a method wherein a lubricant powder is applied on each material contacting surface of a die, an upper punch and a lower punch of a rotary tabletting machine and a molding material is compressed with the lubricated die, upper punch and lower punch (namely an external lubrication method, see JP-B-41-11273, JP-A-56-14098 and JP-A-7-124231).
The tablet production method described in JP-B-41-11273 comprises the steps of charging a fixed amount of material to be tableted in a die, tabletting by compressing the material charged in the die with a pair of an upper punch and a lower punch, and discharging the produced tablet. In a pre-step before charging the molding material in the die, a spray nozzle is provided at a predetermined position above the die for spraying a lubricant, and a lubricant is sprayed from the nozzle to apply the lubricant on a lower surface of the upper punch (“lower surface of upper punch” is called “material contacting surface of upper punch” in this specification) and an upper surface of the lower punch (“lower surface of lower punch” is called “material contacting surface of lower punch” in this specification), both punches corresponding to the die which has come to the position where the nozzle is provided. Then the molding material is charged in the die and is compressed to produce a tablet with the upper punch of which the material contacting surface is applied with the lubricant and the lower punch of which material contacting surface is applied with the lubricant to produce a tablet.
According to the tablet production method described in JP-A-56-14098, in a pre-step before charging a molding material in the die, a diffuser for diffusing a lubricant and a nozzle for spraying air are provided at a predetermined place above a die and a lubricant is diffused on the die which has come to where the diffuser is provided before charging a molding material in the die, thereby placing the lubricant on the material contacting surface of a lower punch provided corresponding to the die. Then a compressed air is injected on the lower punch from the nozzle at the position where the nozzle is provided, thereby blowing up the lubricant placed on the material contacting surface of the lower punch. The blown lubricant is applied on an inner circumference of the die and a material contacting surface of an upper punch. (In this specification “inner circumference of die” is called “material contacting surface of die”. Strictly, “material contacting surface of die” refers to the inner circumferential wall of the die which is above the material contacting surface of the lower punch inserted in a predetermined position in the die.) Next, the molding tablet is produced by compressing the molding material using the die, the upper punch and the lower punch of which material contacting surfaces are applied with a lubricant.
According to the tablet production method described in JP-A-7-124231, a spray chamber connected with a pulsating vibration air generator and provided with a spray nozzle for spraying a lubricant is provided above a die. At a pre-step of charging a molding material in the die, the pulsating vibration air generator is driven to generate a pulsating vibration air in the spray chamber when the die comes to the position where the spray chamber is provided, a lubricant is sprayed from the spray nozzle on each material contacting surface of the die, an upper punch and a lower punch, then the molding material is charged in the die, and the charged molding material is compressed to produce a tablet using the upper punch and the lower punch of which the material contacting surfaces are applied with the lubricant.
Although the production methods disclosed in JP-B-41-11273, JP-A-56-14098 and JP-A-7-124231 are practicable for producing experimentally or producing a small amount of tablets, they have a room for improvement for producing a tablet stably for a long time to meet the requirement of industrial production base.
In addition, the inventors of the present invention have had a fear that in case of constructing a large scale tablet production apparatus suitable for industrial production base, a lubricant powder may cause a dust explosion while producing a tablet with such a apparatus.